The present invention relates to lever switches used in a variety of electronic devices for detecting presence or absence of a recording medium, an operating condition of mechanism, and the like.
A leaf switch, as called commonly, comprised of a movable contact and a stationary contact made of flexible thin sheet metal is known widely as a kind of lever switch for use in a variety of electronic devices for detecting presence or absence of a recording medium such as tape, disk and the like, an operating condition of mechanism, and so on.
One such lever switch of the prior art will be described with reference to FIG. 9 to FIG. 11.
FIG. 9 is a sectioned view depicting a lever switch of the prior art. Box-shaped case 1 made of insulating plastic has an open front and opening 1A in an upper surface. Lever 2 is mounted with shaft 2A to a central portion of the case 1 in a rotatable manner. The lever 2 disposed within the case 1 is provided with actuating parts 2B and 2C at its lower end. Manipulating part 2D at its upper end projects upward from the opening 1A of the case 1.
Movable contact 3 made of flexible thin sheet metal and a pair of stationary contacts 4 also made of flexible thin sheet metal disposed to both sides of the movable contact 3 are inserted and fixed individually in a bottom surface of the case 1 opposite the opening 1A. The movable contact 3 is so disposed that an upper end of it locates between the actuating parts 2B and 2C of the levers 2. The stationary contacts 4 are provided with inwardly curved contacting parts 4A at their upper ends confronting a center area of the movable contact 3. A front face of the case 1, which houses the lever 2, the movable contact 3 and the stationary contacts 4 is covered with a cover (not shown in the figure). The shaft 2A of the lever 2 is thus retained rotatably toward both right and left sides.
In the above-described structure, when the manipulating part 2D of the lever 2 is turned rightward, a lower end of the actuating part 2C turns toward the left side about the shaft 2A as being a fulcrum, as shown in a sectioned view of FIG. 10. This turning movement causes the actuating part 2C to push the upper end of the movable contact 3 and bend it to the left side, so as to render the center area in contact with the contacting part 4A of the left stationary contact 4.
When the manipulating part 2D of the lever 2 is turned further for a predetermined stroke, the upper end of the movable contact 3 shifts further toward the left, and the center area depresses the contacting part 4A, as shown in the sectioned view of FIG. 11. This causes the stationary contact 4 also bend left side, thereby rendering the movable contact 3 and the stationary contact 4 into a state of contacting with each other with a stable contact pressure. When actuating force to the manipulating part 2D is released from the lever 2, resilient returning forces of the movable contact 3 and the stationary contact 4 push the actuating part 2C to the right, and turn the lever 2 in a manner to restore the manipulating part 2D into its neutral position, as shows in FIG. 9.
When the manipulating part 2D of the lever 2 is turned leftward, the actuating part 2B depresses the upper end of the movable contact 3 to the right side, to bend the movable contact 3 to the right, and to make it in contact with the stationary contact 4 on the right side.
However, in the foregoing lever switch of the prior art, the leaf-like movable contact 3 is required to have a length of certain extent in order for it to keep a sufficient permissible stress, since the movable contact 3 is flexed in the right-to-left direction to make it in contact with the stationary contacts 4 at both sides. It is therefore difficult to reduce size of the switch entirely. Furthermore, it also has another problem that conductivity of the contacts tend to became unstable if a stroke given to the lever 2 is small, because of the structure in which a steady contact pressure to the movable contact 3 is obtainable only when the stationary contact 4 is bent after the lever 2 is turned beyond a predetermined amount of stroke.
The present invention addresses the above-described problems of the prior art, and it is intended to provide a lever switch, which realizes downsizing as well as a stable conductivity of contacts.
A lever switch of this invention comprises:
a case (11) having an opening in an upper surface, provided with a common contact and stationary contacts, the common contact being disposed to a center area of a first inner wall of the case, and the stationary contacts being disposed to a second inner wall and a third inner wall opposite each other in the case;
a movable contact (15) having a middle part, first arms extending from both ends of the middle part to a direction of vertical to the first inner wall, turnover parts in continuity with ends of the first arms, second arms in continuity with ends of the turnover parts, and contact points in continuity with the second arms, wherein the middle part (15A) is in contact resiliently with the common contact (12) at all times, and the contact points (15E) are in contact resiliently with the second inner wall and the third inner wall respectively in a slidable manner;
a pair of cams disposed rotatably to a fourth inner wall of the case, lower surface of a depressing part of each of the pair of cams abutting upon respective turnover part of the movable contact; and
a lever disposed rotatably to the fourth inner wall of the case, lower side of the lever abutting on the individual depressing parts of the pair of the cams, and an upper part of the lever projecting through the opening in the case.
In the foregoing structure, a turning movement of the lever causes one of the contact points to make resilient contact with one of the stationary contacts.